Hermeticity requirements of glass to metal and ceramic to metal seals are becoming ever more stringent. Microscopic defects in metal parts used for such seals can severely limit their hermeticity. Heretofore, it has been thought necessary, in those applications in which high hermeticity had to be assured, to use exceptionally pure, clean metal, which requires expensive methods to obtain, such as the vacuum melting of alloys, or vacuum impregnation or pressure impregnation of the metal components. Even with pure metal obtained by such costly methods, it has been found that some terminal components, pins for example, were exhibiting hermetic leak-through.
I have found that such leak-through may be the result of microshrinkage, pipes, seams or laps produced in the reduction process.
One of the objects of this invention is to provide a method of forming a hermetic seal with high hermeticity which substantially eliminates the need for special, costly treatment of metal components, by such methods as vacuum impregnation, pressure impregnation and vacuum melting of alloys.
Another object is to provide such a method and a hermetic seal exhibiting high hermeticity which is simple, economical and highly effective.
Other objects will become apparent to those skilled in the art in the light of the following description.